Method of stabilizing polyphenyl coolants



ing of heat transfer surfaces result. -rnoderator reactors this tendency toward degradation of the fluid after prolonged exposure to radiation and heat 'is controlled by bleeding off a portion of the coolant,

. hour.

3,009,881 METHOD OF STABILIZING POLYPI-ENYL COOLANTS John G. Burr, Tarzana, and Jack D. Strong, Canoga Park, Califi, assignors, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission N Drawing. Filed Nov. 17, 1959, Ser. No. 853,470

3 Claims. (Cl. 252-73) 'and their compatibility with ordinary materials of construction such as carbon steel. Although polyphenyls are among the most stable of organic compounds, they tend to progressively decompose under the effects of heat and nuclear radiations. The, decomposition products are many and complex, and include compounds with molecularweights both lower and higher than of the original polyphenyl compound. Gases are formed, and also higher polymers, for instance hexaphenyl and beyond.

The organic coolant tends to become progressively more viscous with polymer formation, and with continued exposure, decrease of heat transfer coefiicients, increased pumping power requirements, and possibly foul- In the organic and purifying it by distillation. In the distillation the undamaged polyphenyl is separated from polymers and lighter fractions, and is then returned to the reactor together with fresh organic make-up fluid. While such purification and make-up permits the organic reactor to ,operate satisfactorily without adverse effects, an extra cost factor is added. At present, the cost of organic make-up is equivalent to approximately 1 mil per kilowatt This is rather significant when it is noted that average power costs from conventional power sources in the United States are about 6 mils per kilowatt hour, and that the cost of hydroelectric power is about 4 mils per kilowatt hour. fore, that decreasing the rate of polyphenyl breakdown It can be readily appreciated, therein organic moderated reactors could achieve considerable cost savings, improve the operation of the reactor, and make a significant contribution to the development of economical nuclear power from this type of reactor.

An object of our present invention, therefore, is to provide a method of protecting polyphenyls from breakdown under the effects of heat and nuclear radiations.

Another object of our invention is to provide a method of stabilizing an organic reactor coolant.

Still another object is to provide an improved organic reactor coolant composition.

Yet another object is to provide an improved, economical method of decreasing the decomposition rate of polyphenyl coolant undergoing nuclear irradiation.

A further object is to provide an improved polyphenyl reactor coolant composition containing a relatively small amount of a radiation damage inhibitor.

Other objects and advantages of our invention will become apparent from the following detailed description.

In accordance with our present invention we have pro- Patented Nov. 21, 1961 vided a method of inhibiting radiolytic damage to a polyphenyl under nuclear irradiation, which comprises adding a small amount of an aromatic ketone to said polyphenyl. We have found, for example, that adding a few percent of an aromatic ketone to polyphenyl will reduce the hydrogen gas formation and polymer yield in the coolant (measures of polyphenyl decomposition) by as much as about 66%. Aromatic ketone additives are not expensive, are perfectly compatible with the polyphenyl coolant, and have no deleterious effects upon the reactor system or its components.

The polyphenyls now in general use in organic moderated reactors are polyphenyl hydrocarbons containing approximately 2 to 4 phenyl rings, without side-chain substitutions. Diphenyl and terphenyl and its isomers (ortho, meta, para), and mixtures of diphenyl and terphenyl are most widely used. By the term polymer, we intend to designate polyphenyls containing at least five phenyl groups, such polymers being too viscous to be of practical use in a reactor and requiring removal by distillation. The organic moderated reactors are now maintained by distillation at an equilibrium polymer or high boiler residue concentration of about 30%.

We have discovered that the degradation of polyphenyls may be inhibited by adding to the polyphenyl composition a relatively few percent of an aromatic ketone, which We define to be aromatic compound having at least one benzenoid ring and at least one carbonyl grouping attached to the benzenoid ring. The aromatic ketones which maybe used in our invention may be suitably divided into four general sub-generic groupings: benzophenones, para-benzoquinones, 'ortho-benzoquinone's, and benzils; vat dyes of the indanthrenegroup such as violanthrene may also be used. Side-chain substituents may be made to these compounds, although it is generally preferred to employ non-substituted compounds. The substituted members can be fused rings, aryl groups, alkyl groups, oxygen-containing groups such as OH, COOH, CH0 and their derivatives, and non-carbon-containing groups such as halogen, N0 NH and SO H. Any substituent .would generally be aryl groups or fused ring groups, since the non-cyclic substituents tend to be less radiation stable. Furthermore, we prefer the aromatic ketone be composed only of hydrocarbons, with the ex- TABLE Benzophenones Benzophenone Phenyl 4-biphenyl ketone Phenyl-a-naphthyl ketone Di-a-napthyl ketone Di-terphenyl ketone Fluorenone Para-benzoquinones:

Para-benzoquinone Tetraphenyl-para-benzoquinone 1,4-napthaquinone Anthraquinone l-phenylanthraquinone Ortho-benzoquinones:

Ortho-benzoquinone 1,2-benzanthraquinone Phenylbenzanthraquinone 7,8-chrysoquinone 1,2-pyrenequinone 1,2-naphthaquinone 9, lo-phenanthraquinone Benzils:

. Benzil Phenyl benzil Phenyl-u-napthyldiketone Di biphenyl diketone Di-a-naphthyl diketone The following examples are altered to illustrate .our '7 invention in greater detail. 7 a

The irradiations described in the examples below were carried out in a Cobalt-60 (gamma) source with the organic mixture in the liquid state, which was accomplished by heating the mixture to about 90 G and holding it at thistemperature during the course of the irradiation. The samples were contained Within; a Pyrex glass bulb. The sample was degased on a high vacuum line using the conventional freeze-melt technique. For gas measurements, the irradiatedampule was broken in a highvac- 'uum where the products were put through a liquid nitrogen trap. The non-condensable gases at this temperature ('-l96, C.) were collected and measured, and then the gases were analyzed for composition in a mass spectrometer; Total sample weight before irradiations was approximately 8 grams. The Cobalt-60 source intensitywas approximately 1.4 10 electron volts per minute per milliliter of water. Irradiation time was about 48'hours.

Example I Five mole percent. of benzophenone was added to biphenyl and. the irradiation procedure outlined above was followed. The gas evolution was 4.9 10- molecules/ 10.0 e.v., as. compared with 7.8)(10 molecules/109 e.v.-

for a biphenyl control sample.

' Example. 7 Six mole percent of benzophenone was added to terphenyl. The gas evolution rate. was 5l2 10- molecules/ 100. e.v., as compared with 6.6 10 =molecu1es/ 100 e.v.. of ajterphenyl control sample.

Example. Ill

Three mole percent para-benzoquinone was added to a 20%' biphenyl-80% terphenyl mixture. The resulting polymer yield was 75% of the control.

Example IV 7 Nine mole percent ortho-benzoquinone was added to biphenyl. The resulting gas evolution was 3.7 10- molecules/100 e.v., as compared with 7.8 10" molecules/ 1'00 e.v. for the biphenyl control.

Example V Two mole percent ortho-benzoquinone was added to I should be understood to be limited only as indicated in said polyphenyl composition.

an ortho, meta, para-isomeric mixture of terphenyls. The 6 resulting gas evolution .was 3.9 10- molecules/ ev,

as compared with a gas evolution of 4.5 10- molecules/100 e.v. for the terphenyl mixture without the additive. Y i

Example VI 7 Seven mole percent benzil was added to biphenyl. The

resulting gas evolution was 63% of the control sample.

7 Example V II Four mole percent, l-phenylbenzil was added to terphenyl and irradiated. This resulted. in, apolymer yield 78% of the control sample. V

ExampleVIll Two mole percent of 'di-terphenyl ketone was added to a 50-50 mixture of biphenyl and terphenylj. The resulting gas evolution was 83% of the control sample.

v Example IX Ten' mole percent of anthraquinone was added. to biphenyl, and the relative polymer yield was 40% that of biphenyl without the additive.

Example X I 7 About 5 mole percent of benzanthracene-7,l2-dione was added to a 20 mole percent biphenyl-8O mole percent terphenyl mixture, 'andthe. relative gas formation compared to ordinary diphenyl was-74% Example X1: n One mole percent benzoylpyridine was"added to diphenyl and the relative polymer yield was 92%. e

The above examples :are only illustrative, rather than restrictive of our invention. Accordingly, our invention the appended claims. a 1,

"Having thus described our invention, we. claim: v

1. A method of inhibiting radiolyticdamage to a polyphenyl coolant composition undergoing nuclear irradiation, said polyphenylcomposition initially consisting es sentially of polyphenyls having 2-4 phenylj ringspwhich comprises adding to said composition approximately l-lO 1 mole percent of an aromatic ketone selected from. the

group consisting of benzophenones, para-benz oquinones,

ortho-benzoquinones, and benzil'sr 2*.fA method of inhibiting radiolytic damage to a polyphenyl composition undergoing nuclear irradiation, said polyphenyl composition initially consisting essentially of polyphenyls having 2-4 phenylrings, which comprises adding approximately 5 mole percent benzophenone to said polyphenyl composition. I

3. A method of inhibiting radiolytic damage to a poly-- phenyl composition undergoing nuclear irradiation said.

polyphenyl composition initially consistingiessentially of polyphenyls having 2+4 'phenyl rings, whichcomprises adding approximately "5 mole percent anthraquinone to References Cited in the fileof this patent UNITED STATES PATENTS 2,925,448 Golichman. Feb. 16, 1.960

. FOREIGN PATENTS p 7 652,282 Great Britain Apr. 18, 1951 

1. A METHOD OF INHIBITING RADIOLYTIC DAMAGE TO A POLYPHENYL COOLANT COMPOSITION UNDERGOING NUCLEAR IRRADIATION, AND POLYPHENYL COMPOSITION INTITALLY CONSISTING ESSENTIALLY OF POLYPHENYLS HAVING 2-4 PHENYL RINGS, WHICH COMPRISES ADDING TO SAID COMPOSITION APPROXIMATELY 1-10 MOLE PERCENT OF AN AROMATIC KETON SELECTED FROM THE GROUP CONSISTING OF BENZOPHENONES, PARA-BENZOQUINONES, ORTHO-BENZOQUINONES, AND BENZILS. 